Daytime neurocognitive performance is impaired in adolescents and school-age children with sleep-disordered breathing (SDB). Furthermore, animal models of SDB clearly demonstrate that episodic hypoxia during sleep leads to both short-term and long-term decrements in learning and memory, and that these are mediated, at least in part, by oxidant stress. However, the prevalence and neurobehavioral consequences of SDB during the first 2 years of life are unknown. To address this issue, we will examine the hypothesis that infants who develop SDB within their first 7 months will manifest reduced cognitive development by the end of their first year. Furthermore, infants with SDB will show increased oxidant markers in their urine. The following specific aims will therefore be examined: (1) a population survey for the potential presence of SDB will be conducted among 6 month-old infants; (2) Home-based polysomnography will be performed at 7 and 13 months in infants at high risk for SDB and matched controls; and an index of mental development will be administered; (3) The levels of 15-F2t-lsoprostane metabolites in urine will be determined, as correlates for oxidant stress. This longitudinal, prospective study will contribute to our understanding of the prevalence, and neurodevelopmental consequences of SDB in infancy. In addition, it may provide insights into a potential mechanism for this morbidity.